In order to generate the bending motion operated by pressure change in hydrogen gas, soft uni-morph composites were prepared, in which composites dispersed with not only driving particles of LaNi 5 hydrogen storage alloy with Pd-Al 2 O 3 catalyst powders to get high responsiveness, were piled up on a simple polyurethane sheet. Since the highest values of irreversible bending strain at the first hydrogenation (" 1) under 0.3 MPa H 2 gas and the maximum irreversible bending strain during hydrogenation cycles (" m) were remarkably obtained at the 35 vol% of LaNi 5 powders dispersed in polyurethane composites, the bending strain of reversible motion was detected from the first to the 8th hydrogenation (" r 1 and " r 8) under 0.2 MPa H 2 gas. The bending strain of reversible motion of polyurethane composites sheet is more than 2000 ppm, which was approximately equal to that of silicone rubber composites and is extremely larger than that (300 ppm) of ABS resin composites. Responsiveness (d"=dt) of cyclic motion of elastic deformed mover composites, which were constructed with 35 vol%LaNi 5 dispersed powder and matrix of polyurethane or silicone rubber, were more than 10 times higher than that of ABS composite.

Electroactive polymers are widely studied because of their large electrical‐field‐induced strain. Their flexibility and their ability to be deposited on large surfaces make them promising candidates as electroactive materials for actuators or energy‐harvesting devices. For actuation purposes, the material efficiency is directly related to the electrical‐field‐related electrostrictive coefficient M33 through S33 = M33E2, where S33 is the electrical‐field‐induced strain and E is the applied electrical field. Numerous studies concern the increase of M33, but very few have been devoted to its saturations versus electrical field. To this end, the present paper describes the variation of M33 versus thickness, composition, frequency, and electrical field for polyurethane‐based composites. Based on the saturation of the electrical‐field‐induced polarization within the studied polymer composites, a model of the M33 behavior was also proposed, and it was found to show a good agreement with the experimental data. In addition, this model predicts the dielectric constant and the saturation electrical field to be the key parameters ruling the M33 saturation. Copyright © 2011 John Wiley & Sons, Ltd.

The elastocaloric properties of poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] terpolymer were directly characterized using an infrared imaging camera. At a strain of 12%, a reversible adiabatic temperature variation of 2.15 °C was measured, corresponding to an isothermal entropy variation of 21.5 kJ m−3 K−1 or 11 J kg−1 K−1. In comparison with other elastocaloric materials, P(VDF-TrFE-CTFE) appears to represent a trade-off between the large required stresses in shape memory alloys and the large required strains in natural rubber. The internal energy of the P(VDF-TrFE-CTFE) polymer was found to be independent of the strain, resulting in complete conversion of the mechanical work into heat, as for pure elastomeric materials. The elastocaloric effect therefore originates from a pure entropic elasticity, which is likely to be related to the amorphous phase of the polymer only.

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Thanks to their large electrical field-induced strains, electroactive polymers can be used in various applications; as electroactive materials for artificial muscles or as active materials of membranes, due to their flexibility. One drawback concerning their use involves the saturation of the electrical field-induced strain which occurs at around 20% for a polymer film with a thickness of 80 μm. Few studies have been devoted to the understanding of this saturation. To this end, the present paper describes mechanical measurements of the extensive strain versus stress and the determination of the current flowing through an electroactive polymer driven by an electrical field. These experiments have clearly demonstrated that the observed saturation of the electrical induced strain was not due to a mechanical saturation within the sample but to the saturation of the electrically induced polarization. By carrying out a suitable modeling of the polarization versus electrical field, it was possible to calculate the strain and current versus electrical field. These values were then compared to experimental data, and were found to show a very good agreement.